Ethoxylated diamidoamine quaternary of dimethyl sulfate is a well known compound used for the softening of fabric. It is made by reacting a long chain glyceride such as tallow with diethylene triamine at elevated temperatures to produce a diamidoamine represented by the following structure: ##EQU4## wherein R' and R" are long chain alkyl or alkylene groups.
This diamidoamine is then treated with ethylene oxide to give a tertiary amine having the following structure: ##EQU5## wherein R' and R" are long chain alkyl or alkylene groups.
This tertiary amine is then reacted with dimethyl sulfate to prepare the compound represented by the following formula: ##EQU6## wherein R' and R" are long chain alkyl or alkylene groups. This compound is now being used commercially for fabric softening.
This compound has good hydrophilic balance and other characteristics desired in a fabric softening compound. However, it has a serious disadvantage in that under common conditions of use heating is required to maintain the compound fluid and it would be very desirable to have a softening compound like this one which retains all of the desirable attributes of this known compound, but which will remain flowable at lower temperatures.
I have discovered that treating the diamidoamine with propylene oxide instead of ethylene oxide as above referred to I can obtain a compound having the favorable characteristics known to the ethoxylated compound of the art and having in addition the quality of being fluid at substantially lower temperatures.
This discovery is unexpected because it is known that propylene oxide when reacted with amines, acids or alcohols tends to increase the hydrophobic character and oil solubility of the resulting molecule. Further, the longer carbon chain of the propoxy group might be expected to decrease the fluidity of the resulting compound.
In the preparation of the improved diamidoamine quaternary compounds, I may start with the reaction of tallow and diethylene triamine. Or, in the palce of tallow I may use any available source of material which in the reaction will yield alkyl or alkylene radicals having from 10 to 20 carbons in the hydrocarbon chain such as lauric, myristic, palmitic, oleic, linoleic or stearic acids. Conveniently, I can use the common oils such as tallow, lard or other animal or vegetable oils such as corn oil, coconut oil, tall oil or soya oil, or the fatty acid mixtures therefrom, or the fatty acid esters thereof. My improved compounds made from vegetable oils or acids therefrom are useful outside the area of household fabric softeners in fields such as textile treatment or cationic chemistry applications.
The tallow or other fatty oils, or acids or esters above referred to, is reacted with diethylene triamine which is commercially available and in its commercial form may contain small quantities of ethylene diamine and triethylene tetramine.
The reaction may be conducted using about one mole of diethylene triamine to from 0.6 to 0.7 (0.66 preferred) moles of tallow with stirring and using temperatures of about 250.degree. to 300.degree.F. for several hours, after which the resulting reaction product is cooled suitable to below 200.degree.F..
This intermediate product is then reacted with propylene oxide at a temperature of about 180.degree. to 250.degree.F., preferably about 190.degree. to 210.degree.F., with stirring, using propylene oxide in the mole range of 1.0 to 5.0 to 1 mole of the intermediate reaction product to obtain a propoxylated material having the following formula: ##EQU7## where n = 0 to 4.
To a quantity of this propoxylated material may be added a solvent such as isopropanol, ethanol, methanol, diethylene glycol, hexylene glycol, or the like, in a proportion of about 1 part solvent to 10 to 11 parts by weight of the propoxylated material, and dimethyl sulfate in a proportion of about 1 part dimethyl sulfate to about 6 to 10 weight parts of the propoxylated solution in a range of 0.90 to 1.0 moles (preferably 0.95) to 1 mole of the propoxylated reactant material. Good agitation should be provided. Then a further quantity of solvent may be added to give a finished compound of about 90% solids. The resulting product contains the reaction product represented by the following formula: ##EQU8## where n = 0 to 4.
In the reaction between the diamido amine and the propylene oxide one mole of propylene oxide is entered into the reaction, and if further quantities of propylene oxide are available another mole may be entered, and then another, etc., up to about 5 moles in the resulting product.
Where it is desired to obtain a final product having a formula in which n = 0, it may suffice to use propylene oxide in a molar ratio of one mole of propylene oxide to one mole of the intermediate reaction product, but to obtain a reaction product having a formula where n is 1, I may use a molar ratio of propylene oxide to the amine intermediate product of about 2:1. In each case, this ratio will be n = 1 moles of propylene oxide to one mole of the amine.
It is further understood that in most cases, the reaction product may contain mixtures of compounds in which one or more, up to 5 moles of propylene oxide, are added in the reaction, and in which n, in the formula above given, varies from 0 to 4. The addition reaction becomes more difficult as the number of moles of propylene oxide increases. In order to speed this reaction and to facilitate the addition of the larger numbers of moles of propylene oxide it has been found helpful to add small quantities of a caustic catalyst. For example, I may add sodium hydroxide in a proportion of about 0.0005 to 0.002 parts by weight of sodium hydroxide to one part of the reaction mixture.
As above explained, the reaction product may contain a mixture of compounds in which n of the above formula may vary from 0 to 4. I have found that very desirable products may be obtained where the mixture has a predominance of compounds where n is 0, or wherein n is 1. The formula where n = 0 becomes: ##EQU9## and where n is 1, becomes: